1. Field of the Invention
The present invention relates to an automatic placement and routing device for automatically arranging the positions of a plurality of cells and wiring those cells by use of a plurality of nets so as to form a semiconductor integrated circuit (hereinafter may be referred to as a semiconductor IC circuit or Just as a semiconductor IC), and also relates to a method of automatic placement and routing in relation to this device.
2. Description of the Related Art
FIG. 27 is a block diagram showing the configuration of a conventional automatic placement and routing device. In the figure, reference numeral 101 denotes an all-net connection regulator for regulating all the connecting relations between nets and cells into a net list, numeral 102 denotes a cell placement means for arranging the position of cells on the basis of the all-net connecting relations, numeral 103 denotes a global routing means for carrying out a global routing operation with respect to the cells after the placement thereof in accordance with the all-net connecting relations, and numeral 104 denotes a detail routing means for carrying out a detail routing operation with respect to the thus located cells on the basis of the result of the global routing conducted in accordance with the all-net connecting relations.
The operation of the conventional automatic placement and routing device is now explained as below.
FIG. 28 denotes a flow chart showing the conventional method of automatic placement and routing. In the figure, it is shown that first in step ST101, all the relations between nets and cells is regulated into a net list by the all-net connection regulator 101, and thereafter in step ST102, the placement of cells is carried out on the basis of the all-net connecting relations.
Thereafter, in step ST103, a global routing of the thus located cells is performed in accordance with the all-net connecting relations, and then in step ST104, a detail routing of the located cells is performed, again in accordance with the all-net connecting relations.
FIG. 29 is a layout showing the state immediately after the completion of step ST104 of FIG. 28. In the figure, numerals 111 to 114 denote standard cells which are regulated to connect to standard nets, numerals 115 and 116 denote particular cells which are regulated to connect only to variable nets, numeral 117 denotes a pin in the standard cell 111, 118 denotes a pin in the standard cell 112, 119 denotes a pin in the standard cell 113, 1120 denotes a pin in the standard cell 114, numeral 121 and 122 denote pins both in the standard cell 115, numeral 123 and 124 denote pins in the standard cell 116, numeral 125 denotes a wiring physically showing the standard net regulated to connect pins 117 and 118, numeral 126 denotes a wiring physically showing the standard net regulated to connect pins 119 and 120, numeral 127 denotes a wiring physically showing the variable net regulated to connect pins 118 and 124, and numeral 128 denotes a wiring physically showing the variable net regulated to connect pins 119 and 121. The wiring that physically shows the standard net is referred to as a standard wiring, whereas the wiring that physically shows the variable net is referred to as a particular wiring hereinafter. Note that the variable net here means a net whose connecting relation dose not need to be regulated in advance, namely a net which can be freely connected to any one of a plurality of instances of a same master, for example -a net connected to a test pad. On the other hand, the standard net here means a net other than these variable nets.
After all these processes above, a mask is formed on the basis of the thus obtained result of the automatic placement and routing, and a semiconductor IC circuit is formed by used of the thus provided mask. As mentioned above, in the conventional automatic placement and routing device and also the method of placement and routing, the all-net connecting relations are regulated before the placement of cells, and all the cells are disposed at one time. In other words, neither distinction between the variable nets and the standard nets, nor distinction between the particular cells and the standard cells is carried out, and due to this, there have been such problems that the particular wiring physically showing the variable net s made exceptionally long, the complexity of wiring of a semiconductor IC circuit formed by physically showing the standard nets and variable nets is made large, and that the standard wiring receives adverse effects from the particular wiring in terms of signal delay, power consumption, signal integrity and so on.
For example, in FIG. 29, the particular wiring 127 can be made shorter by connecting it to the pin 124. Further, if the cell to be connected is optimized itself and connected to the pin 121 of the particular cell 115, it can be made further shorter.
The present invention has been proposed to solve the problems aforementioned, and it is an object of the present invention to provide an automatic placement and routing device for use in forming a semiconductor integrated circuit, in which the particular wiring is made short, and the complexity of wiring is made small, and also the standard wiring is not likely to receive adverse effects from the particular wiring, and it is also another object of the present invention to obtain a method of automatic placement and routing by use of this device.
An automatic placement and routing device provided for accomplishing the first object of the present invention according to a first aspect thereof is constructed in such a manner that it comprises a standard-net connection regulating means for regulating the connecting relations between the standard nets and the cells into a net list, a cell placement means for arranging the placement of cells on the basis of the connecting relations of the standard nets, and a variable-net connection regulating means for regulating into a net list the connecting relations between the variable nets and the cells whose placement has already been completed.
In the automatic placement and routing device as constructed above, the variable-net connection regulating means regulates the connecting relations between the variable nets and cells on the basis of the result of the cell placement conducted by said cell placement means.
The automatic placement and routing device according to another aspect further comprises a global routing means for executing a global routing with respect to the cells whose placement has already been completed, in accordance with the connecting relations of the standard nets, wherein said variable-net connection regulating means regulates the connecting relation between the variable nets and cells on the basis of the result of the global routing conducted in accordance with the connecting relations of the standard nets.
The automatic placement and routing device according to another aspect further comprises a global routing means for executing a global routing with respect to the cells whose placement has already been completed, in accordance with the connecting relations of the standard nets, and a detail routing means for executing a detail routing with respect to the cells already located, on the basis of the global routing conducted in accordance with the connecting relations of the standard nets, wherein the variable net connection regulating means regulates the connecting relations between the variable nets and the cells on the basis of the result of the detail routing.
The automatic placement and routing device according to another aspect further comprises a global routing means for executing a global routing with respect to the cells whose placement has already been completed, in accordance with the connecting relations of the standard nets and those of the variable nets, and a connection improving means for improving the connecting relations of the variable nets on the basis of the result of the global routing conducted in accordance with the connecting relations of the standard nets and those of the variable nets.
The automatic placement and routing device according to another aspect further comprises a global routing means for executing a global routing with respect to the cells whose placement has already been completed, in accordance with the connecting relations of the standard nets and those of the variable nets, a detail routing means for executing a detail routing with respect to the cells already located, on the basis of the result of the global routing conducted in accordance with the connecting relations of the standard nets and those of the variable nets, and a connection improving means for improving the connecting relations of the variable nets on the basis of the result of the detail routing.
The automatic placement and routing device according to further aspect further comprises a detail routing means for executing a detail routing with respect to the cells whose placement has already been completed, on the basis of the result of the global routing conducted in accordance with the connecting relations of the standard nets and those of the variable nets, and a connection improving means for improving the connecting relations of the variable nets on the basis of the result of the detail routing.
The automatic placement and routing device according to still further comprises a standard-cell placement means for arranging the placement of the standard cells, on the basis of the connecting relations of the standard nets, and a particular cell placement means for arranging the placement of the particular cells outside the area in which the standard cells are disposed.
The automatic placement and routing device according to still further aspect further comprises a global routing means for executing a global routing with respect to the cells whose placement has already been completed, in accordance with the connecting relations of the standard nets, and the particular-cell placement means disposes the particular cells on the basis of the result of the global routing.
A method of automatic placement and routing provided for accomplishing the second object of the present invention comprises a standard-net connection regulating step for regulating the connecting relations between the standard nets and cells into a net list, a cell placement step for arranging the placement of cells on the basis of the connecting relations of the standard nets, and a variable-net connection regulating step for regulating the connecting relations between the variable nets and the cells whose placement has already been completed by said cell placement means.
The method of automatic placement and routing further comprises other steps for executing the operations in connection with each of the members configuring the above-explained automatic placement and routing device.